There is a rotating red light at the ends of the Laser Hazard Zone. If it is on, the laser is operating in the tunnel. If it is off, the laser is not operating in the tunnel.
When the laser is being transported to the FACET tunnel, the curtains are closed. This prevents stray laser light from escaping the laser hazard zone. It is safe to be outside the laser hazard zone when the laser is operating.
Red light on - Laser hazard exists between the curtains.
Red light off- no laser hazard exists.